The present invention concerns a system of one or more implant devices and excitation device, an implant device and a method using the system and one or more devices for the treatment of arterial and venous structures.
The present invention also concerns implant devices, a system of implant devices and external excitation means, and a method for positioning one or more implant devices in a vessel, and subsequently heating these implant devices, preferably simultaneously, thereby transferring heat from implant devices to the vessel's inner wall.
The system, device and method can for example be used for treating atrial arrhythmias, more specific atrial fibrillation (AF), more specific paroxysmal, persistent or permanent. More specifically this invention describes a method that allows to repeatedly create lesions in the heart, more specifically in the atria, more specifically in the left and right atrium, more specifically in the antrum or ostium of the pulmonary veins (PVs). Hereby, the general concept is to implant one or more implant devices into the PVs or other vessels, said implant devices making contact with the vessels' inner walls at the positions where ablation is deemed necessary in order to have PV isolation (PVI). In contrast with prior art, ablation is not performed immediately, but the one or more implant devices can be heated up to a specified temperature by external energy-providing means, which are spatially separated from, i.e. not touching, the implant device and able to provide energy remotely to the implant device for increasing the temperature of the ablation region of the implant device up to an ablation temperature. In a preferred embodiment, an implant device comprises an area which is made from a material which may show magnetic hysteresis and the external energy-providing means are able to create a time-varying magnetic field at the position of the implanted device, hereby heating the implant through the phenomenon of magnetic hysteresis. The maximum temperature the implant device can reach, is limited by the Curie or Néel temperature of the magnetic material used, above which temperature the magnetic hysteresis effect disappears. This Curie or Néel temperature can be engineered precisely to the necessary ablation temperature e.g. by changing the composition of the magnetic alloy that is used. In another embodiment, non-magnetic material may be used, and insulation material may then be used to provide sufficient temperature-controlling means. In an embodiment, the heating of the implant device is done by Joule heating or direct heating, or any other heating system.
The implant device according to the present invention can thus be used inside the heart, both the right and the left side, inside the pulmonary veins, but also if necessary, in arterial and venous structures outside the heart.
The devices, systems and methods as described in this document may also be used in human or animal corpses or in models of human or animal bodies, e.g. for practicing or educational purposes, whereby the heating of the implant devices leaves ablation marks on the vessel's inner wall which can be used to check if the implant devices were positioned correctly and sufficient ablation occurred.
The present document focuses its description on the application of the device inside the heart, both the right and the left side, and inside the pulmonary veins.
A person skilled in the art will be able to interpret the device, the system and the method and to provide them of specific features, components or steps if to be used in other areas.
Human wellbeing is menaced by numerous disorders which change with time. The art of medicine continuously needs to innovate and to adapt to these changes. Despite incessant therapeutic improvements, cardiac disease remains the most important cause of death and hospitalizations in the western society.
Atrial fibrillation, often referred to as AF, is an arrhythmia of the heart causing irregular electrical activity, followed by disorganized and ineffective contractions.
Patients experiencing AF suffer from palpitations, fatigue, severe decrease in quality of life, worsening of heart failure, cerebral stroke, increased mortality and many other symptoms.
Prevalence and incidence of AF is gradually increasing thus causing AF to reach epidemic proportions.
So far, anti-arrhythmic drug treatment for AF is characterized by two major findings: inefficacy and/or intolerable side effects.
The currently available and commonly used drugs to prevent or cure AF can be divided into two groups.
The first group consist of the so-called class-I drugs, betablockers, dronedarone and sotalol.
These drugs have a rather low efficiency ranging between 20 to 40%. Initiating and continuing these drugs requires close monitoring of the patient as these drugs in itself can easily induce life threatening arrhythmias.
The second group consists of only one drug, namely amiodarone, which is the most potent available drug to treat AF.
Its efficiency can range up to 65%. However, the list of possible side effects is practically unlimited: severe thyroid problems, severe lung disease, irreversible tinting of the skin, visual defects, possible carcinogenic nature, etc.
Recently a new invasive treatment modality for atrial fibrillation was discovered when the Bordeaux group of Prof. Dr. Haissaguerre found the pulmonary veins, often referred to as PV's, to be the location of the trigger for AF.
In the following years various techniques were developed to encircle the PV's as an alternative to pharmacological therapy for treating AF.
This technique is called pulmonary vein isolation, often abbreviated as PVI.
The aim was to electrically isolate the triggers in the PV's, assuring not a single electrical connection between the PV's and the left atrium remained.
Soon enough, it was discovered that even a small gap of for example 1 mm in the line encircling the PV's could lead to electrical reconnection of the PV's and hence failure of the procedure with reoccurrence of AF.
Electrophysiology, the art of treating cardiac arrhythmias, is characterized by the use of high-tech equipment to perform diagnostic and therapeutic interventions inside the heart.
Nowadays it is possible to successfully treat virtually every arrhythmia by means of a percutaneous intervention. Nevertheless, curing a patient from AF in a safe and effective manner remains a big hurdle in electrophysiology.
There are two types of procedures by which a PVI can be achieved.
The first group consists of technologies and devices built to encircle the PV's point by point, making sure a continuous line is formed without any gaps.
In most cases a combination is used of a non-fluoroscopic technique to visualize the left atrium with its PV's and a catheter capable of delivering radiofrequency (RF) or cryo-energy.
However, with this first group of procedures, it is not always guaranteed that a continuous line is formed with any gaps. This can occur because the pressure with which an ablating tip is pressed against the wall, the amount of energy transferred from the ablating tip to the wall, the size of the ablation spot on the vessel wall, etc. is not completely under control. In some cases, a gap of the order of 1 mm may already be too wide to ensure a successful outcome of the PVI procedure. In these cases, a repetition of the whole procedure with the accompanying danger, discomfort, cost, etc. for the patient, is usually deemed necessary.
The other group consists of devices created to perform PVI in ‘one single shot’ consecutively in each of the four PV's.
A whole assortment of catheters or sheaths has been conceived: balloon catheters delivering cryo-energy, laser energy, high intensity focused ultrasound, thermal energy, circular catheters delivering pulsed wave RF energy, basket-like catheters delivering RF energy, etc.
PVI has grown from an experimental therapy to a state-of-the-art intervention that can possibly cure AF.
Acute success rates in paroxysmal AF can reach 90% in the most optimal circumstances, with a complication rate around 6%. The most common complication of PVI is cardiac tamponade due to perforation of the left atrium by the ablation catheter.
Usually this can be dealt with by performing a percutaneous puncture of the pericardium with evacuation of the blood, if this proves to be inadequate, a surgical intervention by means of thoracotomy is needed.
The most feared and usually lethal complication is development of a fistula between the oesophagus and the left atrium.
In the past 10 years, catheter ablation techniques in patients with AF have evolved from an initial approach focused on the PV's and their junctions with the left atrium, further often abbreviated as LA, to a more extensive intervention, mainly, but not exclusively, on the LA myocardium and its neuro-vegetative innervation.
It is now recognized that the cornerstone of most catheter and surgical ablation approaches is to isolate the PV's electrically from the LA.
Despite more or less substantial differences among the various catheter techniques that are currently utilized worldwide, results seem to be uniformly similar, with success rates in the range from 50% to 90% depending on the patients and their type of AF (permanent, long-standing persistent, short-standing persistent, or paroxysmal AF).
Frequently a second AF ablation procedure is necessary to improve procedural outcome.
Procedural time to perform a PVI has evolved a great deal in the past years. Initially, point by point PVI regularly could take more than 6 hours.
New imaging techniques shortened these laborious procedures to about four to six hours.
The ‘single-shot’ procedures again are somewhat shorter, but still take two to three hours of procedural time in general.
Fluoroscopy time needed to perform these procedures has equally decreased, but overall ranges between 20-40 minutes.
Because of major discomfort for the patient and the need for the patient to remain motionless during the whole procedure, PVI is performed under general anesthesia in many centers around the world.
The other centers use ‘conscious sedation’ which means the patient is sedated with several different drugs but without the intention to intubate and ventilate the patient.
The need to sedate the patient can cause different harmful side effects.
First of all, general anesthesia always carries a certain mortality risk for the patient. Good ‘conscious sedation’ on the other hand is hard to accomplish.
Under-dosing the drugs leads to patient discomfort and unsolicited patient movement.
Over-dosing the drugs can necessitate switching to general anesthesia during the procedure, which is far from obvious and can even be dangerous in many cases.
The present invention has the intention to conceive a technique which is more acceptable for the patient, less time-consuming, safer and at least equally efficacious in performing PVI.
U.S. Pat. No. 6,632,223 discloses a system for treating atrial fibrillation comprising a stent and a catheter able to deliver the stent near the treatment site. The stent is self-expanding and, once delivered, expands to lodge against the interior wall of the pulmonary vein. The stent can be heated by sending a current through electrical wires in the catheter which are connected to the stent. The thus heated stent may ablate a circumferential blocking lesion of the PV wall. The ablation occurs while the catheter is physically connected to the stent. Therefore, after the ablation, the stent may be disconnected from the catheter and remain in place e.g. to prevent stenosis. This patent does not disclose the possibility of heating the stent by external energy-providing means, i.e. the possibility of heating the stent when it is not physically connected to the catheter. Also, it does not disclose the possibility of using materials which show magnetic hysteresis for at least part of the stent. Thereby, it is not easy to control the ablation temperature of the stent, in fact, the energy delivered to the stent should be monitored very closely as it depends on a multitude of factors, such as the electrical resistance of the stent, the amount and type of electrical current that is sent through the wires, the resistance of these wires, the quality of the thermal contact between stent and vessel wall.
Us patent application 2005/0027306 discloses a catheterization device for delivering a self-expanding stent. The device has an inner shaft and an outer shaft moveable with respect to the inner shaft. The self-expanding stent is received on the inner shaft adjacent its distal end. A tapered tip is located on the inner shaft distal end and it forms a smooth transition from the delivery device to a guidewire extending therethrough. A handle allows a practitioner to deploy the stent single handedly. The stent may have its segments in a first radial configuration for delivery of the stent or the stent may have a plurality of segments in a first radial configuration and a plurality of second segments in a second radial position.
US patent application 2005/0101946 discloses another method and system for treating AF by ablation of a pulmonary vein, using a stent which has a resonant circuit. The stent can be implanted at the site of ablation and subsequently activated by external energy-providing means, in particular by an electromagnetic field with the resonating frequency of the resonant circuit of the stent. The application does not disclose the possibility of using materials which show magnetic hysteresis for at least part of the stent, and to use the hysteresis effect for activating the stent. Thereby, it is also in this way not easy to control the ablation temperature of the stent. The energy delivered to the stent should be monitored very closely as it depends on a multitude of factors and the temperature of the stent is not under control, such as the electrical resistance of the stent and the resonant circuit of the stent, the magnitude of the RF field at the site of the stent, the quality of the thermal contact between stent and vessel wall.
European patent application EP 1 036 574 discloses a device and method for heating an implanted stent up to a certain temperature, using external energy-providing means. The stent can be heated up through the effect of magnetic hysteresis. However, in this patent application, the temperature is controlled by an external controlling system which measures the temperature of the stent via e.g. an infrared camera, and alters the energy provided with the external energy-providing means accordingly. Hereby, it is not explicitly disclosed that the system is used for ablation. Furthermore, the temperature is controlled by an external feedback system, and not e.g. by the material properties of the stent. Moreover, European patent application EP 1 036 574 does not disclose that the stent or implant may subtend at least a substantially complete circumferential band of the vessel's inner wall.
U.S. Pat. No. 7,235,096 discloses an implantable stent for treating a damaged body lumen, which comprises tubular stent body having several interconnected microholes distributed throughout the body uniformally along the entire length of the body. The tubular stent body has several interconnected microholes distributed throughout the stent body substantially uniformally along the entire length of the stent body; the several microholes are small so as to promote an organized growth pattern of infiltrating cells throughout the stent body, and the stent body is otherwise substantially free of holes larger than the microholes; the stent body is formed from a fibrous three dimensional non-woven matrix. The patent also discloses a stent system comprising the stent in spaced juxtaposition to an energy source for transcutaneously applying energy to the stent, thereby causing the temperature of the stent to increase to a temperature above body temperature (preferably 38-49° C.). It further discloses an active stent comprising the stent and further comprising live cells growing in the interconnected microholes. A method for measuring flow of a fluid through a body lumen is disclosed, involving: implanting the stent into a body lumen having a flow of fluid through it; energizing the implanted stent transcutaneously to raise its temperature above body temperature; monitoring transcutaneously the output from at least one of the temperature sensors upon cessation of the energizing to determine the cooling rate at each of the at least one sensor: and obtaining the flow rate of the fluid through the stent from the cooling rate at the at least one sensor. Also disclosed is a method for treating a tubular body organ in a subject involving: promoting the ingrowth of living cells in the stent; and implanting the stent into the tubular organ of the subject prior to or following promoting the ingrowth of the living cells so as to treat the tubular organ, whereby the stent body is formed from a fibrous three dimensional non-woven matrix.
In U.S. Pat. No. 7,235,096, the temperature of the stent can be controlled by an at least partially external control system. In this case, the temperature sensor or sensors transmit the measured temperature to said external control system, which then controls the external energy source. Further, in this patent, the temperature of the stent can be controlled by the use of material with a Curie temperature whereby the heating of the stent occurs via hysteresis heating. Hereby the temperature of the stent is limited to the Curie temperature, since the mechanism of hysteresis heating only works below the Curie temperature. Both temperature control mechanisms, i.e. the external control system and the use of magnetic materials, have their shortcomings.
The mechanism comprising the external control system leads to the necessity of a dedicated external energy source, specifically adapted for receiving the temperature from the temperature sensor. Furthermore, in such a system the energy source, which in most cases will be a radiofrequent field, will need to be controlled in intensity and possibly also in frequency in order for the implant to be kept at a desired temperature.
The mechanism of hysteresis heating has a number of difficulties, especially in finding the correct alloy with an optimal Curie temperature. As this optimal temperature may be different case-by-case, a different alloy may need to be found for different temperatures.
There remains a need in the art for improved devices, systems and methods for the ablation of a substantially complete circumferential band around a vessel's wall from the inside. The present invention aims to resolve at least some of the problems mentioned above, e.g. to make sure that the ablation is performed for a substantially complete circumferential band around a vessel's wall from the inside, that the ablation itself can be triggered with external means and this multiple times if necessary, that the ablation temperature is well under control and does not depend on less-controlled elements in the treatment or on an intricate monitoring system, etc.
The present invention tries to overcome the problems by providing an implant with a built-in temperature control means, whereby said control means are capable of keeping the temperature of at least part of the implant to or below a desired temperature. The present invention also provides a system and method for heating an implant to or up to a desired maximal temperature.